Field of the Invention
The present invention relates to a seatbelt retractor to retract a webbing of a seat belt onto a spool.
Related Background of the Invention
A vehicle such as an automobile is usually provided with a seatbelt apparatus having a retractor for protecting a passenger on a seat. The retractor includes a spool for allowing a webbing (seatbelt) to be extracted therefrom or retracted thereon and a locking mechanism to prevent rotation of the spool in an extracting direction of the webbing in response to an acceleration or inclination of the vehicle or an acceleration of extraction of the webbing (seatbelt) in an emergency (such as collision).
In an emergency, the retractor actuates the locking mechanism to lock (or prevent) extraction of the webbing from the spool so that the passenger wearing the webbing is restrained on a seat and is thus prevented from being thrown out of the seat.
This lock of extraction of the webbing is released by utilizing a function of the retractor that retracts the webbing by the spool when the locked webbing is loosened (i.e., when a force in the extracting direction is released) (refer to Patent Literature 1).
In other words, specifically, in an emergency, a clutch is connected to a locking gear integrally coupled to the spool (winding shaft of the webbing) of the seatbelt retractor (hereinafter simply referred to as retractor) while the spool is rotating in an extracting direction of the webbing. When the clutch rotates in the extracting direction of the webbing due to the connection, a pawl is moved in conjunction with the rotation of the clutch and engages with a ratchet gear integrally coupled to the spool. This prevents the spool (winding shaft) of the retractor from rotating in the extracting direction.
In order to release a lock state where the pawl engages the ratchet gear, the connection between the clutch and the locking gear is required to be released. More specifically, when the webbing is retracted, the spool rotates in the retracting direction of the webbing, and the clutch, which is biased by a return spring in the retracting direction, integrally rotates in the retracting direction of the webbing with the locking gear. In conjunction with this rotation of the clutch, the pawl is rotated in a direction to disengage from the ratchet gear (unengaging direction). The rotation of the clutch is stopped as the pawl returns to an initial position (rest position), and the spool then further retracts the webbing, making the locking gear rotate in the retracting direction of the webbing. Whereby the locking gear rotates relatively with respect to the clutch and releases the connection between the locking gear and the clutch. Thus, the amount of rotation of the spool from the beginning to the end of the unlocking operation of the locking mechanism is larger than the amount of rotation of the spool from the beginning to the end of the locking operation of the locking mechanism, correspondingly making it necessary to retract a longer length of the webbing.
As described above, in a conventional retractor, a quick unlocking operation of the locking mechanism is difficult. Thus, when retraction of the webbing necessary for releasing the connection between the clutch and the locking gear is difficult to execute, in such a case as when an end lock occurs, in which the spool is suddenly stopped due to completion of storage of whole amount of the webbing, the end lock causes the clutch to be connected to the locking gear and thus to prevent rotation of the spool in the extraction direction of the webbing, it is difficult to release the lock. Also, when the locking mechanism is unexpectedly actuated by acceleration of a vehicle or movement of a passenger in ordinary use, retraction of a large length of the webbing for releasing the lock of extraction of the webbing is time-consuming, so user sometimes feels to be troublesome to release the lock.